﻿/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

using System;

namespace Aliyun.Acs.Core.Retry.BackoffStrategy
{
    public class ExponentialBackoffStrategy : IAlibabaBackoffStrategy
    {
        private const int MaxRetryLimit = 30;
        private readonly int baseDelayInMilliseconds;
        private readonly int maxDelayInMilliseconds;

        public ExponentialBackoffStrategy()
        {
        }

        public ExponentialBackoffStrategy(int baseDelayInMilliseconds, int maxDelayInMilliseconds)
        {
            this.baseDelayInMilliseconds = baseDelayInMilliseconds;
            this.maxDelayInMilliseconds = maxDelayInMilliseconds;
        }

        public int GetDelayTimeBeforeNextRetry(RetryPolicyContext retryPolicyContext)
        {
            var retries = Math.Min(MaxRetryLimit, retryPolicyContext.RetryAttemptTimes);
            var delay = Math.Min(maxDelayInMilliseconds, baseDelayInMilliseconds << retries);

            return delay;
        }
    }
}
